50 EDWARD C. DAY 



effects are readily seen to be the four already mentioned: in 

 15'' the number of beats jumps from 30 to 57, in 18- from 30 to 

 54; in 15^ the initial rate drops from 58 to 42, in 18^ from 53 to 51, 

 and in both instances the acceleration crops out and tends to 

 reach a maximum nearer the middle of the series than was 

 possible in the shorter normal series. The dorsad series of 15^ 

 exhibits, as a result of severing the nerves, a very marked increase 

 in the number of beats from 21 in the preceding normal series to 

 126, and also a decided speeding up in the rate of beat from 61 to 

 44 seconds for the initial 10 beats. The maximum rate is attained 

 early in the series at the end of the third 10 beats. In 18-, 

 whereas there is little change in rate, there is an increase in 

 length of the series from 38 to 54 beats. 



Extirpation of the ganglion produces effects similar to those 

 wrought by paring the tunic and severing nerves. They are 

 quickly apparent from a study of graphs 15", 16^, and 18\ 

 The number of beats for the ventrad series increases in the three 

 graphs from 25 to 83, 27 to 85, and 42 to 65, respectively; for the 

 dorsad series from 23 to 54, 25 to 95, and from 41 to 58. The 

 increase in acceleration, as indicated by the difference in the 

 number of seconds required for the initial 10 beats, for the ventrad 

 series is 14", 13", and 4", respectively, and for the dorsad series 

 11", 9", and 8" for the three graphs under consideration. The 

 duration of the three ventrad series lengthens from 2' 29" to 

 6' 21", 2' 27" to 5', and from 3' 52" to 5' 10", the three dorsad 

 series from 2' 11 " to 3' 52", 2' 19" to 6', and from 3' 39" to 4' 41 ". 

 There is further a shortening of the pause between the ventrad 

 and dorsad series. Owing to irregularities attendant upon the 

 choice of a landmark for observing the pulsations, the average 

 of two successive pauses is selected for comparison rather than 

 single pauses. In graphs 15'^ and 18-^ the averages are 8" and 

 10.5", respectively. No average could be obtained for graph 16^ 

 owing to interruption of the observations before the dorsad 

 series was completed. The single pause recorded, however, is 

 3 " less than that for the previous normal series. Thus, not only 

 do the individual beats follow each other in more rapid sequence, 

 but each series of beats succeeds the one preceding at a shorter 



